I very rarely have this popup on start:

Thought, the app started apparently correctly. No idea if this is important for you to know @dmarmor
[EDIT]
After that i closed the app to edit something in it. This then appeared:

Ideen the app had a size of 500MB.

• I run the scan --> nothing to fix
• Check the activity monitor --> no App running
• Tried to start the app --> A short "jump" in the dock, then nothing
• Try to edit it again: still the same error message ("app running")
• Deleted the Payload dir --> no better
• Recovered from the backup --> app still doesn't start (!!)
• Recovered the payload dir --> not better
• Try to edit --> Worked. Edited something for the app to be rebuild --> Icon disappeared in the finder! Although correct in the edit wizard. --> It started an empty app with that default icon
• Closed. The app still 500MB and no app running in the activity monitor
• Rebooted the mac --> Finally i could edit it again and start it. But now i'm on this app in the same situation as in Custom icon keeps disappearing #290 (so no way to get its icon back)